The research of new derivatives of 2,2-dimethyl-cyclopropanecarboxylic acid gets an impulse by the fact that 2,2-dimethyl-3-isobutenyl-cyclopropanecarboxylic acid (chrysanthemic acid) esterified with a retronolone (2-alkenyl-3-methyl-cyclopent-2-en-4-olone), constitutes pyrethrum, an insecticide of a natural origin edowed with very positive characteristics such as for instance a high and fast insecticide action by contact on winged insects, and a low toxicity on mammals by mouth together with a negligible dermic toxicity.
However, the particular structure of the molecule makes pyrethrum easily degradable and therefore makes its action non-persistent, this latter characteristic not allowing its use for the protection of agricultural cultivations, thus limiting its use only for indoor applications.
Part of the research of new synthetic pyrethroids, that is, of substances which, by recalling the structure of pryethrum, are equally endowed with both a high insecticide activity as well as with a very low toxicity for mammals while showing, however, improved stability characteristics, has been directed towards the study of new derivatives of 2,2-dimethyl-cyclopropanecarboxylic acid.
There are known many derivatives substituted in position 3of the cyclopropyl ring (see, for instance, Synthetic Pyrethroids (M. Elliot Ed.) ACS Symposium Series No. 42, Washington 1977). However, the most promising, from the point of view of the stability, are those derivatives that carry in position 3 a .beta., .beta.-dihalovinyl group (J. Farkas et al., Chem. Listy 52, 688 (1958); M. Elliott et al., Nature (London) 246, 169 (1973); M. Elliott et al., J. Chem. Soc., Perkin 1, 1974, 2470).